1. Field of the Invention
The present invention relates to a pulsation dampening apparatus and a clutch master cylinder which are used for a hydraulic clutch operation system such as a clutch actuator of a vehicle. More specifically, the present invention relates to a technology to absorb or dampen pulsations or undue vibrations in a hydraulic fluid of a hydraulic circuit of the hydraulic clutch operation system.
2. Description of the Related Art
Hydraulic clutch actuators of a vehicle are known for operating a clutch mechanism by way of a clutch master cylinder connected through a conduit to a slave cylinder by a driver of the vehicle. The hydraulic clutch actuators are filled with hydraulic fluid such that, when the piston of the clutch master cylinder is actuated, the slave cylinder which is fastened to a bell housing of the clutch is simultaneously actuated so as to operate a clutch lever or a release fork of the clutch by displacement of the hydraulic fluid from the clutch master cylinder to the slave cylinder through the conduit.
The hydraulic clutch actuator of this type operates the clutch in such a way that, when the driver of the vehicle depresses the clutch pedal, the clutch master cylinder is so actuated that the slave cylinder pushes the clutch lever to disengage the clutch. While when the driver releases the clutch pedal, the slave cylinder releases the clutch lever and therefore the clutch is engaged.
In such operations, the hydraulic clutch actuator is filled with hydraulic oil in high pressure when the clutch master cylinder is actuated by depression of the clutch pedal. While imbalances in the crank shaft of the vehicle engine or engine firing impulses are transmitted to the flywheel which undergoes a swashing movement, the flywheel swashing movement in turn leads to vibrations of the diaphragm spring of the clutch release mechanism, the vibrations of the diaphragm spring are transferred to the release bearing of the clutch, and the vibrations propagate backwardly through the hydraulic fluid in the slave cylinder, through the hydraulic fluid in the conduit interconnecting the slave cylinder and the clutch master cylinder, through the hydraulic fluid in the clutch master cylinder, and then through the clutch master cylinder pushrod to the clutch pedal where they are experienced by the driver as vibrations of the clutch pedal. Such vibrations, which are called herein after “pulsations” make the diver irritated.
Various devices have been proposed in an attempt to attenuate these pulsations. Japanese Examined Utility Model publication No.03-14581 discloses a hydraulic clutch actuator with a pulsation absorbing apparatus, as shown in FIG. 1.
Referring to FIG. 1, the hydraulic clutch actuator includes a clutch master cylinder 120, a reservoir tank 121 integral with the clutch master cylinder 120 to supply the hydraulic fluid to a pressure chamber 122 formed in the clutch master cylinder 120, a pulsation absorbing apparatus 140 integral with the clutch master cylinder 120.
The clutch master cylinder 120 has known parts such as a flange 123 to attachment of the clutch master cylinder 120 to the vehicle, a piston 124 in the chamber 122, a connecting rod 125 to operate the piston 124 by the driver, a return spring 126 of the piston 124, and a check valve 127 connected through a passage 128 with the reservoir tank 121 to allow the supply of hydraulic fluid from the reservoir tank 121 to the chamber 122 while to prevent the hydraulic fluid in the chamber 122 form returning back to the reservoir tank 121.
The pulsation absorbing apparatus 140 has a cylindrical housing 141 perpendicularly projecting downward from the clutch master cylinder 120. The main housing 141 defines a dampening chamber 142 communicated through a passage 143 with the chamber 122 in the clutch master cylinder 120. The cylindrical housing 141 has an absorbing assembly having a piston mechanism 144 perpendicularly reciprocate in the dampening chamber 141, a conical spring 145 urging the piston mechanism 144 to make a space between the passage 145 and the piston cup 144a of the piston mechanisms 144, a first dampening plate 146 contacting the bottom of the piston mechanism 144, a second dampening plate 147 sealing the bottom portion of the main housing 141, screws 148 to fix the second dampening plate 147 to the bottom of the main housing 141, and a damper disc 149 disposed between first and second dampening plates 147 and 148.
In operation, the hydraulic fluid in the pressure chamber 122 of the clutch master cylinder 120 is also filled in the dampening chamber 142. When the pulsations are propagated to the hydraulic fluid, the pulsations transfer to the piston mechanism 144 and are absorbed by deformations of the first and second dampening plates 146 and 147 and the damper disc 149. However, the deforming movements of these members 146, 147, and 149 of the first prior art undergo the undue vibrations of the screws 148. Thus, the screws 148 may loosen in use of the apparatus.
Another prior art, Japanese unexamined patent publication No.2000-2270 is shown in FIGS. 2 and 3.
In the following, substantially equivalent elements are designated by the same reference numerals, and duplicated description thereof will be omitted.
Referring to FIG. 2, a clutch master cylinder 120 has a connecting sleeve 129 perpendicularly projecting downward. The connecting sleeve 129 supports a pulsation dampening apparatus 150 interconnecting the chamber 122 and the dampening chamber 142 through the passage 143.
Referring to FIG. 3, the pulsation dampening apparatus 150 has a joint sleeve 151 which is inserted in the connecting sleeve 129 to attachment of the pulsation dampening apparatus 150, a disc body 152 integrally and coaxially formed with the bottom portion of the joint sleeve 151 to support an absorbing assembly 153 having disc members 154 and 155. The absorbing assembly 153 is attached by a thin flange 156 which is deformed to inner peripheral annular shape by the caulking process.
Because the absorbing assembly 153 is supported by the thin flange 156 in the second prior art, assembling process may be difficult when the caulking process is conducted by a press machine. Furthermore, material of the thin flange 156 must be thin and extensible, so that the material of the disc body 152 may be limited. This makes the pulsation dampening apparatus 150 different parts from the cylinder body of the clutch master cylinder 120. Thus, the assembly process of the pulsation dampening apparatus 150 to the clutch master cylinder 120 would be necessary in this aspect, and therefore the clutch master cylinder 120 of the second prior art would be made in high cost.